Power tongs are often employed when connecting or disconnecting tubular members for oilfield applications. Conventional power tongs typically have a ring gear which rotates independently of two cage plates. See for example U.S. Pat. No. 5,291,808. The cage plates are bolted together as one assembly and rotate freely about the body of the tong while the ring gear is connected to the gear train within the tong. Within the ring gear is typically a set of jaw members (or jaws) which are used to grip the tubular section being rotated by the power tong. In most cases, these jaw members include a set of rollers and pins. The rollers engage and rotate against a cam surface on the ring gear, thus, moving the jaw members inward toward the tubular. The rotation of the ring gear causes the jaw members to move inward due to the cage plate assembly being initially held stationary by a brake band or other mechanism. The jaw members engage the tubular and bite until the friction of the brake band holding the cage plates is overcome. Thereafter, the cage plate assembly rotates with the ring gear as one mechanism and applies torque to the tubular.
Example jaw members may be seen in U.S. Pat. Nos. 5,819,605 and 7,017,450 (the '450 patent). FIG. 1A illustrates a rear view of a jaw member 1 having a jaw body 2 with upper and lower flange sections 3A and 3B and a roller cavity 4. Jaw roller 5 fits partially within jaw cavity 4 and roller pin 6 is inserted through the aperture 7 in upper flange section 3A, roller aperture 10, and aperture 7 in lower flange section 3B, thus fixing roller 3 within jaw cavity 4, but allowing roller 3 to rotate relative to jaw body 2. FIG. 1A also illustrates how roller pin 6 has a crown section 8 and upper flange section 3A includes a counter-sunk shoulder 9 so that when roller pin 6 is inserted into jaw member 1, the top surface of crown section 8 is approximately flush with the top surface of upper flange section 3A.
Upper and lower flange sections 3A and 3B can take any shape as long as the flange sections allow a portion of jaw roller 5 to extend from jaw body 2 and engage the ring gear's cam surface. For example, FIG. 7 in the '450 patent illustrates flange sections having a somewhat different shape but serving the same function. Likewise, FIG. 1(a) and FIG. 5 of the '450 patent illustrate additional jaw designs and different shapes the flange sections 3A and 3B may take. FIG. 7 of the '450 patent also shows how jaw members 1 will have a gripping surface general opposite jaw roller 5. The gripping surface may take many shapes, but in FIG. 7 of the '450 patent, the gripping surface is formed of strip dies 307.
The jaw and pin combination is used to provide a high strength, low friction mechanism to contact and move along the cam surface of the ring gear. Many conventional jaws may use a retainer mechanism to hold the pin in place while the roller is free to rotate about the pin. Such mechanisms include, but are not limited to, snap rings such as seen in FIG. 1B, screws such as seen in FIG. 1C, and tack welding the pin to the jaw flange (not illustrated). Pins are generally retained against downward movement by way of a crown section. The retainer mechanisms used often prevent axial and rotational movement of the pins (e.g., screws and tack welding). Pins with no retainers other than the crown section may also used which allow for rotational movement of the pin but do not safeguard against the pin being inadvertently knocked upward out of the jaw member (and potentially falling into the well bore).